It's hard to compare but maybe Alen can show of some stats for a previous year and this one.
I'll show you the stats, but they won't prove anything else but the fact that we're talking about two extremely special players.
The bare facts that at 23 and 22 these two guys won the CL as their team's best players, were CL's topscorers, scored in the final and won the ballon d'or tell a lot.
There are great players, some are the greatest, but to me, from the players i've seen, only three are the greatest of the greatest: Maradona, Ronaldo and Zidane. Baggio and Ronaldinho are among the greatest but imo not on the same level as the above three. Messi and Cristiano will surely join on that 3 men list and make it a 5 men list.
But I'd like to mention one special quality that Messi posses and i've never seen it done by anyone else. Imagine having an imaginary ball adhered to your foot. You run with it but the others can't see the ball and the ball isn't running away from you because it's glued. That's the impression I get when I watch Messi running with the ball, just that the ball isn't imaginary and it isn't adhered to his foot.
Anyway, as for the stats:
2009/2010
Messi: 23 goals and 9 assists on 30 matches. In total
32 goals+assists on 30 matches (La Liga+CL+other cups)
Ronaldo: 17 goals and 1 assist on 17 matches. In total
18 goals+assists on 17 matches .
2008/2009
Messi: 38 goals+18 assists on 51 matches. In total
56 goal+assists on 51 match
Ronaldo: 26 goals+9 assists on 53 matches. In total
35 goals+assists on 53 matches
2007/08
Messi: 16 goals+13 assists on 40 matches. In total
29 goals+assists on 40 matches
Ronaldo: 42 goals +9 assists on 49 matches. In total
51 goal+assists on 49 matches.
For the last 3 seasons:
Messi : 117 goals+assists on 121 matches (77 goals+40 assists)
Ronaldo: 104 goals+assists on 119 matches (85 goals+19 assists)